The statements in this section merely provide background information related to the present teachings and may not constitute prior art.
Various types of power tools comprise a cutting tool or bit that is raised or lowered relative to a base that rests on or against the workpiece. Often the tool or bit is attached to the output shaft of a motor unit that can be vertically or axially moved relative to the base. Movement of the motor unit and attached tool bit relative to the base unit determines the depth of cut into the workpiece.
Routers, including some laminate trimmers, are constructed according to this basic design. The router bit is attached to the motor output spindle by means of a tool holder such as a collet or chuck and the bit projects through an opening in the base to contact the workpiece. The motor unit is mounted to the base by means that allow the operator to move the motor and bit axially relative to the base in order to determine the depth of cut of the bit. Router base and depth of cut systems fall into two commonly recognized categories. They are plunge-base routers and fixed-base routers (including so-called D-handle bases). Generally speaking, plunge routers comprise a generally planar base element, a motor unit, and a plurality of support columns on which the motor unit is vertically movably mounted above the base. Usually, the motor unit is biased upward or away from the base. Means are provided for finely adjusting the depth of cut and for locking the motor unit at the selected depth/height against the biasing force.
Fixed-base routers usually comprise a generally cylindrical base and a motor unit with a cylindrical housing portion. The cylindrical portion of the motor housing fits snugly but movably within an annulus of the cylindrical portion of the base with the motor spindle and router bit projecting downward beyond the lowest portion of the base. The cylindrical portion of the base often includes a longitudinal or axial cut or gap that permits the base diameter to expand or contract slightly under the force of a clamp mechanism that bridges the gap and that can be used to tighten the base onto the motor housing within. Means for adjusting the depth of cut by adjusting the vertical or axial position of the motor unit and bit within the base are also provided. The base clamp is loosened for adjusting the cutting depth and after the desired depth is set with the depth adjusting means the base clamp is tightened to lock the motor housing at the set position.
The typical base is made from a one-piece casting. The use of a one-piece casting requires that multiple surfaces be machined to accommodate the various components and features, such as the adjustment ring and the motor housing. Additionally, the multiple machined surfaces are required to allow precise positioning of the power tool relative to the base. The machining of multiple surfaces can be time-consuming, require intricate tooling, and/or increase the overall cost of the base. Thus, it would be advantageous to provide a base requiring less machined surfaces. Additionally, the use of a single, one-piece casting results in a base of a single material. In order to provide the desired strength for the base, the thickness of the base may be required to be large. This large size may make handling of the base and the tool awkward and/or inconvenient. Additionally, in the typical base, the anti-rotation feature is a separate component that is attached to the base. The use of a separate anti-rotation feature is an additional assembly step, can require an additional machining operation, and is an additional cost in the production of the base. Thus, it may be advantageous to provide a base requiring less machining operations and also which may be more convenient to use. Additionally, it would be advantageous if the cost of producing the base could be reduced.